Cataract extraction is a frequently performed surgical procedure. A cataract forms through opacification of the eye's crystalline lens. The cataract scatters light passing through the lens, and may perceptibly degrade vision. Generally, a cataract can vary in degree from slight to complete opacity. Early in the development of an age-related cataract, the power of the lens may increase, causing near-sightedness (myopia). Over time, the gradual yellowing and opacification of the lens may reduce the perception of blue colors as shorter wavelengths are more strongly absorbed and scattered within the cataractous crystalline lens. As the cataract formation gradually progresses, the patient may experience progressive vision loss.
Cataract treatment may involve surgically removing the opaque crystalline lens, and replacing it with an artificial intraocular lens (IOL). Each year, an estimated 15 million cataract surgeries are performed worldwide. Cataract surgery can be performed using a technique called phacoemulsification in which an ultrasonic tip with associated irrigation and aspiration ports is used to sculpt the relatively hard nucleus of the lens to facilitate removal through an opening made in the anterior lens capsule. The nucleus of the crystalline lens is contained within an outer membrane of the lens referred to as the lens capsule. To access the lens nucleus, surgeons first perform a manual continuous curvilinear capsulohexis (CCC) procedure to form a circular hole in the anterior side of the lens capsule. Alternatively, surgeons may use a laser surgical system to perform the anterior capsulotomy to gain access to the lens nucleus. The surgical laser beam may also be used to fragment the cataractous crystalline lens before it is aspirated out of the eye. After the cataractous lens is removed, a synthetic foldable intraocular lens (IOL) can be inserted into the remaining lens capsule of the eye.
Planning a cataract treatment can be challenging. There is significant variation between patients in many important eye biometric parameters, each of which may affect surgical planning, treatment, and outcome. Moreover, many patients may have biometric configurations, including for example, corneal lower order and higher order aberrations, extreme axial lengths, and/or previous conical refractive treatments such as LASIK, which may also affect surgical planning, treatment, and outcome. For example, with respect to eye aberrations, some patients have near-sightedness (myopia), far-sightedness (hyperopia), or astigmatism. Near-sightedness occurs when light focuses in front of the retina, while far-sightedness occurs when light refracts to a focus behind the retina. Astigmatism occurs when the corneal curvature is unequal in two or more directions. Various surgical methods have been developed and used to treat these types of aberrations. Ideally, for best results and outcome, a cataract surgeon would have access to not only ocular biometry information, but also to information on the eye's anterior corneal surface, posterior conical surface, anterior lens surface, posterior lens surface, lens tilt, lens thickness, and lens position in order to plan cataract treatment pre-operatively, and/or to assess the post-operative refractive state of a patient's eye with the implanted IOL.
A variety of optical diagnostic systems have been developed, each of which provides a limited subset of the desired measurements. Thus, currently most patients have various measurements performed on different devices if the measurements are taken at all. There is a significant disadvantage, however, to using multiple measurement devices in cataract planning because the patient's eye may be in different positions during each of the measurements, and/or it may have changed between the different measurements, or the measurement may have been made under different conditions. Further, there may be no way to combine or fuse the data sets from different devices to obtain a single, three-dimensional model of the patient's eye. Hence, it can be often difficult to apply advanced vision modeling techniques, such as ray tracing, because the current diagnostic environment is often inadequate to reliably produce the three-dimensional models necessary for accurate vision modeling.
As a result, there is an ongoing need for an improved optical imaging, measurement, and diagnostic system that can obtain most, if not all, of the necessary biometric and structural features of a patient's eye with the patient's eye in a single orientation within a brief period of time, that can fuse the data obtained from various optical techniques to achieve an accurate three-dimensional model of a patient's eye, and that can utilize advanced vision modeling techniques, such as ray tracing or other power calculation techniques, to improve cataract planning and outcome evaluation.